Monday, November 2, 2009

Preferred Hardware for Virtualization - Dell 2900 III & Dell T610

I understand that not everyone is going to agree with this post. I don't really expect them to. When designing a system there are many variables, and the best solution will not always be the same solution. However, in my current position, I have done the analysis many times for different projects and for some reason, I almost always come back to the same hardware. So, I figured I would share the reasons why I usually end up purchasing these servers for my virtualization needs.

Obviously it all boils down to value and functionality. I feel that these servers deliver great performance at a great price and they are functional in ways that fit our needs. Ok, first I will discuss the downside to these servers so that I can explain why, for me, it doesn't matter. The downside is that these servers are a whopping 5U. Yeah, I know, that is a lot of rack space for a server these days. However, if you are just starting down the virtualization path, you will usually find that you have more than enough rack space, and if not, there are definitely other solutions that will save you the space.

Now, if you are familiar with Dell hardware, you may have overlooked these. In order to find them, you usually need to select tower servers and most medium to large organizations do not browse that area of the Dell website. Even though they are listed in the tower server section, both of these servers have optional rack configurations (Last time I checked, they took away the rack config for the 2900 III, but I am sure you can still get it if you have an account rep or call in).

Alright, so why am I listing two different models? The T610 is basically the replacement for the 2900 III and supports the latest Intel processors. The price is not much more than the 2900 so if you have the need for faster processing you may want to skip the 2900, but because there is a slight cost savings, because there is one nice feature that the T610 does not have, and because most people would be surprised how little processing power their servers actually need I have included it. So, what is the feature that has saved the 2900? Dell calls it a flex bay. Basically, the flex bay allows you to fit two extra drives in the server that are either mirrored or striped. These drives can be used to run the OS so that you don't have to steal drives from the main Raid controller or partition a section of your array for the OS. Unfortunately, as of last time I checked, the T610 does not offer a flex bay.

Ok, I guess I should move on to the stuff that really matters. Here are the specs that make these servers my preferred choice for virtualization:

Dell 2900 IIICPUDual socket. Supports two dual-core (52xx) or quad-core (54xx) CPUs. When it comes to virtualization, I always go with the fastest processor with the greatest number of cores (within reason). The main reason for this is OS licensing as I will explain later.

Memory12 DIMMs. That's right 12. So, you can add 48 GB (12 X 4GB) of memory to the server.

Hard DrivesUp to 8 X 3.5 inch SATA or SAS drives (One of my next posts is going to be titled, 'The Case for Direct-Attached Storage (DAS)'. I will link to it here when I am done.). I know that some people will argue that 2.5 inch drives are faster, but if the 3.5 inch drives are fast enough, as of today, they are still cheaper and are available in larger capacities. What does all this mean? Well for under $5,800 you can get 8 X 450 GB 15k SAS drives, giving you around 3.5 terrabytes of raw storage (the Raid controller is limited so you will not be able to use all of it, but the next step down is 300 GB 15k drives (2.34 TB raw) and it only saves you a few hundred dollars)

Flex BayTwo more for a total of 10 3.5 inch SATA or SAS drives (Note: these cannot be added to the 8 drive array)

Memory12 DIMMs (RDIMM or UDIMM). That's right 12. But, this model is slightly different in that you can only use 6 DIMMs per processor. However, you can get 8 GB sticks of RAM. So, for a single processor you can have up to 48 GB and for two processors up to 96 GB. If you are cost concious though, you will probably stick to the 4 GB sticks which cuts those numbers in half.